Role of the 2B4 Receptor in CD8+ T-Cell-Dependent Immune Control of Epstein-Barr Virus Infection in Mice With Reconstituted Human Immune System Components

Patients with X-linked lymphoproliferative (XLP) disease due to deficiency in the adaptor molecule signaling lymphocytic activation molecule-associated protein (SAP) are highly susceptible to one specific viral pathogen, the Epstein-Barr virus (EBV). This susceptibility might result from impaired CD8+ T-cell and natural killer cell responses to EBV infection in these patients. We demonstrate that antibody blocking of the SAP-dependent 2B4 receptor is sufficient to induce XLP-like aggravation of EBV disease in mice with reconstituted human immune system components. CD8+ T cells require 2B4 for EBV-specific immune control, because 2B4 blockade after CD8+ T-cell depletion did not further aggravate symptoms of EBV infectio

PD/1-PD-Ls Checkpoint: Insight on the Potential Role of NK Cells

The identification of inhibitory NK cell receptors specific for HLA-I molecules (KIRs and NKG2A) provided the molecular basis for clarifying the mechanism by which NK cells kill transformed cells while sparing normal cells. The direct interactions between inhibitory NK cell receptors and their HLA-I ligands enable NK cells to distinguish healthy from transformed cells, which frequently show an altered expression of HLA-I molecules. Indeed, NK cells can kill cancer cells that have lost, or under express, HLA-I molecules, but not cells maintaining their expression. In this last case, it is possible to use anti-KIR or anti-NKG2A monoclonal antibodies to block the inhibitory signals generated by these receptors and to restore the anti-tumor NK cell activity. These treatments fall within the context of the new immunotherapeutic strategies known as "immune checkpoint blockade." These antibodies are currently used in clinical trials in the treatment of both hematological and solid tumors. However, a more complex scenario has recently emerged. For example, NK cells can also express additional immune checkpoints, including PD-1, that was originally described on T lymphocytes, and whose ligands (PD-Ls) are usually overexpressed on tumor cells. Thus, it appears that the activation of NK cells and their potentially harmful effector functions are under the control of different immune checkpoints and their simultaneous expression could provide additional levels of suppression to anti-tumor NK cell responses. This review is focused on PD-1 immune checkpoint in NK cells, its potential role in immunosuppression, and the therapeutic strategies to recover NK cell cytotoxicity and anti-tumor effect

Editorial: NK Cell Subsets in Health and Disease: New Developments

Natural killer (NK) cells were discovered ca 1975, as the first group of lymphoid cells that were neither T cells nor B cells. Since then, the dissection of the biology of NK cells has been growing exponentially with many seminal discoveries from the identification of MHC class I-specific inhibitory receptors to the discovery of receptor\u2013ligand pairs involved in NK cell activation and to the manipulation of NK cells in cancer. In this research topic, we asked a group of thought leaders in NK cell biology to review recent advances in their origins and biology, and their roles in cancer, infection, and inflammation. Together, these 25 articles provide a timely survey of NK cells as critical immunologic components of health and disease. They will hopefully prompt further dialog and developments in basic and translational immunology

Case Report: A Peculiar Case of Inflammatory Colitis After SARS-CoV-2 Infection

open14noWe report a case of inflammatory colitis after SARS-CoV-2 infection in a patient with no additional co-morbidity who died within three weeks of hospitalization. As it is becoming increasingly clear that SARS-CoV-2 infection can cause immunological alterations, we investigated the expression of the inhibitory checkpoint PD-1 and its ligand PD-L1 to explore the potential role of this axis in the break of self-tolerance. The presence of the SARS-CoV-2 virus in colon tissue was demonstrated by qRT-PCR and immunohistochemical localization of the nucleocapsid protein. Expression of lymphocyte markers, PD-1, and PD-L1 in colon tissue was investigated by IHC. SARSCoV- 2-immunoreactive cells were detected both in the ulcerated and non-ulcerated mucosal areas. Compared to healthy tissue, where PD-1 is weakly expressed and PD-L1 is absent, PD-1 and PD-L1 expression appears in the inflamed mucosal tissue, as expected, but was mainly confined to non-ulcerative areas. At the same time, these markers were virtually undetectable in areas of mucosal ulceration. Our data show an alteration of the PD-1/PD-L1 axis and suggest a link between SARS-CoV-2 infection and an aberrant autoinflammatory response due to concomitant breakdown of the PD-1/ PD-L1 interaction leading to early death of the patient.openRutigliani, Mariangela; Bozzo, Matteo; Barberis, Andrea; Greppi, Marco; Anelli, Emanuela; Castellaro, Luca; Bonsignore, Alessandro; Azzinnaro, Antonio; Pesce, Silvia; Filauro, Marco; Rollandi, Gian Andrea; Castagnola, Patrizio; Candiani, Simona; Marcenaro, EmanuelaRutigliani, Mariangela; Bozzo, Matteo; Barberis, Andrea; Greppi, Marco; Anelli, Emanuela; Castellaro, Luca; Bonsignore, Alessandro; Azzinnaro, Antonio; Pesce, Silvia; Filauro, Marco; Rollandi, Gian Andrea; Castagnola, Patrizio; Candiani, Simona; Marcenaro, Emanuel

Case report: Variable response to immunotherapy in ovarian cancer: Our experience within the current state of the art

: Despite recent advances in ovarian cancer (OC) treatment, including the introduction of bevacizumab and PARP-inhibitors, OC remains a lethal disease. Other therapeutic options are being explored, such as immunotherapy (IT), which has been proved effective in many solid tumors. Findings about tumor-infiltrating cytotoxic and regulatory T cells, together with the expression of PD-1 on immune cells and of PD-L1 on tumor cells, gave the rationale for an attempt to the use of IT also in OC. We treated two patients with avelumab, an anti-PD-L1 monoclonal antibody, after the first line of chemotherapy: Patient A underwent 19 cycles of maintenance therapy with avelumab with a disease-free interval of 12 months, whereas patient B showed a slight progression of disease after only eight cycles. A higher PD-L1 expression in tumor cells of patient A was detected. She also underwent a genomic assessment that described the presence of a high Tumor Mutational Burden (TMB) and a status of Loss of Heterozygosity (LoH). This different response to the same treatment puts in evidence that some genomic and immune features might be investigated

Harnessing NK Cells for Cancer Treatment

In the last years, natural killer (NK) cell-based immunotherapy has emerged as a promising therapeutic approach for solid tumors and hematological malignancies. NK cells are innate lymphocytes with an array of functional competences, including anti-cancer, anti-viral, and anti-graft-vs.-host disease potential. The intriguing idea of harnessing such potent innate immune system effectors for cancer treatment led to the development of clinical trials based on the adoptive therapy of NK cells or on the use of monoclonal antibodies targeting the main NK cell immune checkpoints. Indeed, checkpoint immunotherapy that targets inhibitory receptors of T cells, reversing their functional blocking, marked a breakthrough in anticancer therapy, opening new approaches for cancer immunotherapy and resulted in extensive research on immune checkpoints. However, the clinical efficacy of T cell-based immunotherapy presents a series of limitations, including the inability of T cells to recognize and kill HLA-Ineg tumor cells. For these reasons, new strategies for cancer immunotherapy are now focusing on NK cells. Blockade with NK cell checkpoint inhibitors that reverse their functional block may overcome the limitations of T cell-based immunotherapy, mainly against HLA-Ineg tumor targets. Here, we discuss recent anti-tumor approaches based on mAb-mediated blocking of immune checkpoints (either restricted to NK cells or shared with T cells), used either as a single agent or in combination with other compounds, that have demonstrated promising clinical responses in both solid tumors and hematological malignancie

New miRNA Signature Heralds Human NK Cell Subsets at Different Maturation Steps: Involvement of miR-146a-5p in the Regulation of KIR Expression

Natural killer cells are cytotoxic innate lymphoid cells that play an important role for early host defenses against infectious pathogens and surveillance against tumor. In humans, NK cells may be divided in various subsets on the basis of the relative CD56 expression and of the low-affinity FcγRIIIA CD16. In particular, the two main NK cell subsets are represented by the CD56bright/CD16−/dim and the CD56dim/CD16bright NK cells. Experimental evidences indicate that CD56bright and CD56dim NK cells represent different maturative stages of the NK cell developmental pathway. We identified multiple miRNAs differentially expressed in CD56bright/CD16− and CD56dim/CD16bright NK cells using both univariate and multivariate analyses. Among these, we found a few miRNAs with a consistent differential expression in the two NK cell subsets, and with an intermediate expression in the CD56bright/CD16dim NK cell subset, representing a transitional step of maturation of NK cells. These analyses allowed us to establish the existence of a miRNA signature able to efficiently discriminate the two main NK cell subsets regardless of their surface phenotype. In addition, by analyzing the putative targets of representative miRNAs we show that hsa-miR-146a-5p, may be involved in the regulation of killer Ig-like receptor (KIR) expression. These results contribute to a better understanding of the physiologic significance of miRNAs in the regulation of the development/function of human NK cells. Moreover, our results suggest that hsa-miR-146a-5p targeting, resulting in KIR down-regulation, may be exploited to generate/increment the effect of NK KIR-mismatching against HLA-class I+ tumor cells and thus improve the NK-mediated anti-tumor activity

Identification of a novel cord blood NK cell subpopulation expressing functional programmed death receptor-1

BackgroundNatural Killer cells (NKs) represent the innate counterpart of TCRαβ lymphocytes and are characterized by a high anti-tumor and an anti-viral cytotoxic activity. Recently, it has been demonstrated that NKs can express PD-1 as an additional inhibitory receptor. Specifically, PD-1 was identified on a subpopulation of terminally differentiated NKs from healthy adults with previous HCMV infection. So far it is unknown whether PD-1 appears during NK-cell development and whether this process is directly or indirectly related to HCMV infection.MethodsIn this study, we analyzed the expression and function of PD-1 on Cord Blood derived NKs (CB-NKs) on a large cohort of newborns through multiparametric cytofluorimetric analysis.ResultsWe identified PD-1 on CB-NKs in more than of half the newborns analyzed. PD-1 was present on CD56dim NKs, and particularly abundant on CD56neg NKs, but only rarely present on CD56bright NKs. Importantly, unlike in adult healthy donors, in CB-NKs PD-1 is co-expressed not only with KIR, but also with NKG2A. PD-1 expression was independent of HCMV mother seropositivity and occurs in the absence of HCMV infection/reactivation during pregnancy. Notably, PD-1 expressed on CB-NKs was functional and mediated negative signals when triggered.ConclusionTo our understanding, this study is the first to report PD-1 expression on CB derived NKs and its features in perinatal conditions. These data may prove important in selecting the most suitable CB derived NK cell population for the development of different immunotherapeutic treatments

Uptake of CCR7 by KIR2DS4+ NK cells is induced upon recognition of certain HLA-C alleles: implication of activating KIRs in haploidentical HSCT

Alloreactive NK cells have been shown to play a crucial role in the successful therapy of high risk acute leukemias in the haplo-HSCT setting (1-4). Recently, we have shown that in KIR/KIR-ligand mismatched haplo-HCT a remarkable advantage may exist in selecting KIR2DS1+ donors to be used in C2+ recipients, not only for their killing capability against recipient’s leukemic cells, but also for their ability of killing allogeneic DC and T cell blasts, thus preventing GvHD and graft rejection. Moreover we have shown that, as previously described for KIR2DS1, also KIR2DS4, another activating KIR, may induce acquisition of CCR7 and migratory properties by human NK cells interacting with B-EBV infected cells expressing spe- cific HLA molecules. Importantly, this de novo CCR7 expression, occurring by a mech- anism of trogocytosis, may represent a mechanism by which alloreactive KIR2DS1+ or KIR2DS4+ NK cells can migrate to lymph nodes, kill recipient’s DCs and prevent priming of alloreactive donor’s T cells as well as induction of graft-versus-host dis- ease (GvHD)

PD-1 in human NK cells: evidence of cytoplasmic mRNA and protein expression

Under physiological conditions, PD-1/PD-L1 interactions regulate unwanted over-reactions of immune cells and contribute to maintain peripheral tolerance. However, in tumor microenvironment, this interaction may greatly compromise the immune-mediated anti-tumor activity. PD-1 + NK cells have been detected in high percentage in peripheral blood and ascitic fluid of ovarian carcinoma patients. To acquire information on PD-1 expression and physiology in human NK cells, we analyzed whether PD-1 mRNA and protein are present in resting, surface PD-1 12 , NK cells from healthy donors. Both different splicing isoforms of PD-1 mRNA and a cytoplasmic pool of PD-1 protein were detected. Similar results were obtained also from both in vitro-activated and tumor-associated NK cells. PD-1 mRNA and protein were higher in CD56 dim than in CD56 bright NK cells. Confocal microscopy analyses revealed that PD-1 protein is present in virtually all NK cells analyzed. The present findings are compatible with a rapid surface expression of PD-1 in NK cells in response to appropriate, still undefined, stimuli